Method for producing and purifying p-nitrophenol

Abstract

The invention discloses a method for producing and purifying p-nitrophenol, and belongs to the field of chemical preparation. Comprising the following steps: S1, mixing p-nitrochlorobenzene and a sodium hydroxide aqueous solution under the protection of inert gas, heating and stirring, and filtering after reaction to obtain a reaction solution; adding an organic solvent into the reaction liquid, extracting and separating to obtain an organic phase and a water phase, cooling and crystallizing the water phase, and performing centrifugal suction filtration to obtain filtrate and sodium p-nitrophenolate; s2, uniformly mixing sodium p-nitrophenolate with hot water under the protection of inert gas, adding a hydrochloric acid aqueous solution, adjusting the pH value, heating and stirring, cooling and stirring, cooling and crystallizing, and carrying out centrifugal suction filtration to obtain a p-nitrophenol crude product; and carrying out reduced pressure distillation on the p-nitrophenol crude product to obtain p-nitrophenol. The sodium p-nitrophenolate and the p-nitrophenol prepared by the method provided by the invention are high in yield and purity, and have a good application prospect in the field of chemical preparation.

Description

Technical Field

[0001] The present invention belongs to the field of chemical preparation, and particularly relates to a method for the production and purification of p-nitrophenol. Background Art

[0002] p-Nitrophenol is a colorless to light yellow crystalline powder with an odor similar to bitter almonds. It is soluble in hot water, alcohol, and ether. Under normal circumstances, its structure is stable. It is an important fine chemical intermediate, mainly used for the production of p-aminophenol, an intermediate for paracetamol. At present, p-nitrophenol is mostly produced by using p-nitrochlorobenzene, caustic soda, and hydrochloric acid as raw materials. Through hydrolysis reaction, crystallization, primary separation, slurry adjustment, acidification reaction, and secondary separation, p-nitrophenol is generated. A large amount of mother liquor containing sodium chloride is produced during the separation and centrifugation. Due to the relatively high temperature of the hydrolysis reaction, tar is produced to varying degrees in each batch of reactions. Its main components are incompletely hydrolyzed p-nitrochlorobenzene, hydroquinone, and aromatic ethers. The generated tar will enter the subsequent brine refining section with the mother liquor.

[0003] The patent application with the publication number CN 101759570 A discloses a method for the preparation of p-nitrophenol. It includes the following process steps: hydrolysis reaction: putting p-nitrochlorobenzene and caustic soda into a hydrolysis kettle, heating and continuously stirring to obtain a reactant; crystallization; primary separation; slurry adjustment; acidification reaction; secondary separation. The method for the preparation of p-nitrophenol provided by this application has a relatively high yield of p-nitrophenol prepared, but still inevitably produces tar during the reaction process, which affects the subsequent treatment. How to separate the tar and further purify p-nitrophenol is an urgent problem to be solved. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for the production and purification of p-nitrophenol to achieve the purpose of purifying p-nitrophenol.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A method for the production and purification of p-nitrophenol includes the following steps:

[0007] S1. Under the protection of an inert gas, mix p-nitrochlorobenzene and an aqueous sodium hydroxide solution, heat and stir. After the reaction is completed, filter to obtain a reaction solution; add an organic solvent to the reaction solution, extract and separate to obtain an organic phase and an aqueous phase. Cool the aqueous phase to crystallize, and centrifugally filter to obtain a filtrate and sodium p-nitrophenolate;

[0008] S2. Under the protection of an inert gas, uniformly mix sodium p-nitrophenolate with hot water, add an aqueous hydrochloric acid solution, adjust the pH, heat and stir, cool and stir, cool to crystallize, and centrifugally filter to obtain a crude p-nitrophenol product; subject the crude p-nitrophenol product to vacuum distillation to obtain p-nitrophenol.

[0009] Further, the heating temperature is 150 - 170°C; the reaction time is 3 - 4 h.

[0010] Further, the size of the filter membrane for filtration is 0.8 - 3 μm.

[0011] Further, the volume of the organic solvent is 10% - 15% of the volume of the reaction solution; the organic solvent is one of ether and ethyl acetate; both the organic phase and the filtrate can be recycled.

[0012] Further, in S1, the crystallization by cooling the aqueous phase is to cool to 10 - 20°C for crystallization.

[0013] Further, the concentration of the hydrochloric acid aqueous solution is 25% - 35%; the pH is adjusted to 1 - 2.

[0014] Further, the stirring during heating is carried out at 60 - 80°C for 0.5 - 1 h; the stirring during cooling is carried out after cooling to 40 - 45°C for 0.5 - 1 h.

[0015] Further, in S2, the crystallization by cooling is to cool to 20 - 30°C for crystallization.

[0016] Further, the pressure of the vacuum distillation is 0.05 - 0.08 MPa.

[0017] Advantages of the present invention:

[0018] (1) The present invention provides a method for the production and purification of p-nitrophenol. The original sedimentation is changed to active coke discharging. First, sodium p-nitrophenolate and tar are separated to reduce the impurities generated by subsequent continuous side reactions; then p-nitrophenol is purified. The fractional coke discharging can not only improve the reaction efficiency and save time, but also improve the product quality and reduce the service life of subsequent consumables.

[0019] (2) The active coke discharging method adopted by the present invention combines filtration - extraction - crystallization in the synthesis of sodium p-nitrophenolate; the filtration method replaces the traditional time-consuming and laborious sedimentation method. The filtration step mainly removes the macromolecular polymers formed by the polymerization of p-nitro under high temperature; the organic solvent extraction method is used to separate the small molecule tar insoluble in water; then the crystallization by cooling is used to precipitate sodium p-nitrophenolate, which not only achieves the separation of sodium p-nitrophenolate and tar, reduces a series of side reactions generated by tar in subsequent reactions, but also removes the unreacted sodium hydroxide, reduces the dosage of subsequent hydrochloric acid solution, reduces the generation amount of high-salt wastewater, and reduces the cost.

[0020] (3) The active coke discharging method adopted in the present invention, after cooling and crystallization to precipitate during the synthesis of p-nitrophenol, is purified by vacuum distillation, which improves the distillation efficiency, reduces the loss during the purification process, and improves the purity of p-nitrophenol. Detailed implementation manners

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0022] Embodiment 1

[0023] This embodiment provides a method for the production and purification of p-nitrophenol, including the following steps:

[0024] S1. Under the protection of inert gas, p-nitrochlorobenzene and aqueous sodium hydroxide solution are mixed, heated to 160 °C and stirred for 4 h. After the reaction is completed, filtration is carried out. The size of the filter membrane is 1.5 μm to obtain a reaction solution; 15% of the volume of the reaction solution of ether is added to the reaction solution, and extraction and separation are carried out to obtain an organic phase and an aqueous phase. The aqueous phase is cooled to 15 °C and then crystallized, and centrifugal filtration is carried out to obtain a filtrate and sodium p-nitrophenolate; both the organic phase and the filtrate can be recycled;

[0025] S2. Under the protection of inert gas, sodium p-nitrophenolate and hot water are mixed evenly, 30% hydrochloric acid aqueous solution is added, the pH is adjusted to 1.5, the temperature is raised to 80 °C and stirred for 0.5 h, then cooled to 40 °C and stirred for 0.5 h, and cooled to 25 °C for crystallization, and centrifugal filtration is carried out to obtain crude p-nitrophenol; the crude p-nitrophenol is vacuum distilled at 0.06 MPa to obtain p-nitrophenol.

[0026] Embodiment 2

[0027] Compared with Embodiment 1, the difference in this embodiment is that "the size of the filter membrane is 1.5 μm" in S1 is changed to "the size of the filter membrane is 0.8 μm", and the specific implementation steps are as follows:

[0028] S1. Under the protection of inert gas, p-nitrochlorobenzene and aqueous sodium hydroxide solution are mixed, heated to 160 °C and stirred for 4 h. After the reaction is completed, filtration is carried out. The size of the filter membrane is 0.8 μm to obtain a reaction solution; 15% of the volume of the reaction solution of ether is added to the reaction solution, and extraction and separation are carried out to obtain an organic phase and an aqueous phase. The aqueous phase is cooled to 15 °C and then crystallized, and centrifugal filtration is carried out to obtain a filtrate and sodium p-nitrophenolate; both the organic phase and the filtrate can be recycled;

[0029] S2. Under the protection of inert gas, mix sodium p-nitrophenolate with hot water evenly, add 30% hydrochloric acid aqueous solution, adjust the pH to 1.5, raise the temperature to 80 °C and stir for 0.5 h, then lower the temperature to 40 °C and stir for 0.5 h, cool down to 25 °C for crystallization, and centrifuge and filter to obtain the crude p-nitrophenol; subject the crude p-nitrophenol to vacuum distillation at 0.06 MPa to obtain p-nitrophenol.

[0030] The remaining raw materials and the preparation process are the same as those in Example 1.

[0031] Example 3

[0032] The difference between this example and Example 1 is that in S1, “the size of the filter membrane is 1.5 μm” is changed to “the size of the filter membrane is 3 μm”. The specific implementation steps are as follows:

[0033] S1. Under the protection of inert gas, mix p-nitrochlorobenzene and sodium hydroxide aqueous solution, heat to 160 °C and stir for 4 h. After the reaction ends, filter with a filter membrane of 3 μm size to obtain the reaction solution; add 15% of the volume of the reaction solution of ether to the reaction solution, extract and separate to obtain the organic phase and the aqueous phase. Cool the aqueous phase to 15 °C for crystallization, and centrifuge and filter to obtain the filtrate and sodium p-nitrophenolate; both the organic phase and the filtrate can be recycled.

[0034] S2. Under the protection of inert gas, mix sodium p-nitrophenolate with hot water evenly, add 30% hydrochloric acid aqueous solution, adjust the pH to 1.5, raise the temperature to 80 °C and stir for 0.5 h, then lower the temperature to 40 °C and stir for 0.5 h, cool down to 25 °C for crystallization, and centrifuge and filter to obtain the crude p-nitrophenol; subject the crude p-nitrophenol to vacuum distillation at 0.06 MPa to obtain p-nitrophenol.

[0035] The remaining raw materials and the preparation process are the same as those in Example 1.

[0036] Example 4

[0037] The difference between this example and Example 1 is that in S1, “15% of the volume of the reaction solution of ether” is changed to “10% of the volume of the reaction solution of ether”.

[0038] S1. Under the protection of inert gas, mix p-nitrochlorobenzene and sodium hydroxide aqueous solution, heat to 160 °C and stir for 4 h. After the reaction ends, filter with a filter membrane of 1.5 μm size to obtain the reaction solution; add 10% of the volume of the reaction solution of ether to the reaction solution, extract and separate to obtain the organic phase and the aqueous phase. Cool the aqueous phase to 15 °C for crystallization, and centrifuge and filter to obtain the filtrate and sodium p-nitrophenolate; both the organic phase and the filtrate can be recycled.

[0039] S2. Under the protection of inert gas, mix sodium p-nitrophenolate with hot water evenly, add 30% hydrochloric acid aqueous solution, adjust the pH to 1.5, raise the temperature to 80 °C and stir for 0.5 h, then cool down to 40 °C and stir for 0.5 h, cool down to 25 °C for crystallization, and centrifuge and filter to obtain crude p-nitrophenol; Distill the crude p-nitrophenol under reduced pressure at 0.06 MPa to obtain p-nitrophenol.

[0040] The remaining raw materials and the preparation process are the same as those in Example 1.

[0041] Example 5

[0042] The difference between this example and Example 1 is that "ethyl ether" in S1 is changed to "ethyl acetate", and the specific implementation steps are as follows:

[0043] S1. Under the protection of inert gas, mix p-nitrochlorobenzene and sodium hydroxide aqueous solution, heat to 160 °C and stir for 4 h. After the reaction is completed, filter. The size of the filter membrane is 1.5 μm to obtain the reaction solution; Add 15% of the volume of the reaction solution of ethyl acetate to the reaction solution, extract and separate to obtain the organic phase and the aqueous phase. Cool the aqueous phase to 15 °C for crystallization, and centrifuge and filter to obtain the filtrate and sodium p-nitrophenolate; Both the organic phase and the filtrate can be recycled;

[0044] S2. Under the protection of inert gas, mix sodium p-nitrophenolate with hot water evenly, add 30% hydrochloric acid aqueous solution, adjust the pH to 1.5, raise the temperature to 80 °C and stir for 0.5 h, then cool down to 40 °C and stir for 0.5 h, cool down to 25 °C for crystallization, and centrifuge and filter to obtain crude p-nitrophenol; Distill the crude p-nitrophenol under reduced pressure at 0.06 MPa to obtain p-nitrophenol.

[0045] The remaining raw materials and the preparation process are the same as those in Example 1.

[0046] Example 6

[0047] The difference between this example and Example 1 is that "distillation under reduced pressure at 0.06 MPa" in S2 is changed to "distillation under reduced pressure at 0.08 MPa", and the specific implementation steps are as follows:

[0048] S1. Under the protection of inert gas, mix p-nitrochlorobenzene and sodium hydroxide aqueous solution, heat to 160 °C and stir for 4 h. After the reaction is completed, filter. The size of the filter membrane is 1.5 μm to obtain the reaction solution; Add 15% of the volume of the reaction solution of ethyl ether to the reaction solution, extract and separate to obtain the organic phase and the aqueous phase. Cool the aqueous phase to 15 °C for crystallization, and centrifuge and filter to obtain the filtrate and sodium p-nitrophenolate; Both the organic phase and the filtrate can be recycled;

[0049] S2. Under the protection of inert gas, mix sodium p-nitrophenolate with hot water evenly, add 30% hydrochloric acid aqueous solution, adjust the pH to 1.5, heat up to 80 °C and stir for 0.5 h, then cool down to 40 °C and stir for 0.5 h, and cool down to 25 °C for crystallization. Centrifuge and filter to obtain the crude p-nitrophenol; Distill the crude p-nitrophenol under reduced pressure at 0.08 MPa to obtain p-nitrophenol.

[0050] The remaining raw materials and the preparation process are the same as those in Example 1.

[0051] Comparative Example 1

[0052] Compared with Example 1, this comparative example is different in that filtration is not carried out in S1. The specific implementation steps of S1 are as follows:

[0053] S1. Under the protection of inert gas, mix p-nitrochlorobenzene with aqueous sodium hydroxide solution, heat up to 160 °C and stir for 4 h to obtain a reaction solution; Add 15% of the volume of the reaction solution of diethyl ether to the reaction solution, extract and separate to obtain an organic phase and an aqueous phase. Cool the aqueous phase to 15 °C for crystallization, centrifuge and filter to obtain a filtrate and sodium p-nitrophenolate; Both the organic phase and the filtrate can be recycled.

[0054] The remaining raw materials and the preparation process are the same as those in Example 1.

[0055] Comparative Example 2

[0056] Compared with Example 1, this comparative example is different in that extraction is not carried out in S1. The specific implementation steps of S1 are as follows:

[0057] S1. Under the protection of inert gas, mix p-nitrochlorobenzene with aqueous sodium hydroxide solution, heat up to 160 °C and stir for 4 h. After the reaction is completed, filter with a filter membrane of 1.5 μm to obtain a reaction solution; Cool down to 15 °C for crystallization, centrifuge and filter to obtain a filtrate and sodium p-nitrophenolate; The filtrate can be recycled.

[0058] The remaining raw materials and the preparation process are the same as those in Example 1.

[0059] Comparative Example 3

[0060] Compared with Example 1, this comparative example is different in that neither filtration nor extraction is carried out in S1. The specific implementation steps of S1 are as follows:

[0061] S1. Under the protection of inert gas, mix p-nitrochlorobenzene with aqueous sodium hydroxide solution, heat up to 160 °C and stir for 4 h. After the reaction is completed, cool down to 15 °C for crystallization, centrifuge and filter to obtain a filtrate and sodium p-nitrophenolate; The filtrate can be recycled.

[0062] The remaining raw materials and the preparation process are the same as those in Example 1.

[0063] Comparative Example 4

[0064] This comparative example is different from Example 1 in that filtration - extraction - crystallization is not carried out in S1. The specific implementation steps are as follows:

[0065] S1. Under the protection of inert gas, p - nitrochlorobenzene and aqueous sodium hydroxide solution are mixed, heated to 160 °C and stirred for 4 h. After the reaction ends, a mixed solution of sodium p - nitrophenolate is obtained;

[0066] S2. Under the protection of inert gas, the mixed solution of sodium p - nitrophenolate is mixed evenly with hot water, 30% aqueous hydrochloric acid solution is added, the pH is adjusted to 1.5, the temperature is raised to 80 °C and stirred for 0.5 h, then cooled to 40 °C and stirred for 0.5 h, and then cooled to 25 °C for crystallization. After centrifugal filtration, crude p - nitrophenol is obtained; The crude p - nitrophenol is distilled under reduced pressure at 0.06 MPa to obtain p - nitrophenol.

[0067] The remaining raw materials and preparation process are the same as those in Example 1.

[0068] Comparative Example 5

[0069] This comparative example is different from Example 1 in that vacuum distillation is not carried out in S2. The specific implementation steps of S2 are as follows:

[0070] S2. Under the protection of inert gas, sodium p - nitrophenolate is mixed evenly with hot water, 30% aqueous hydrochloric acid solution is added, the pH is adjusted to 1.5, the temperature is raised to 80 °C and stirred for 0.5 h, then cooled to 40 °C and stirred for 0.5 h, and then cooled to 25 °C for crystallization. After centrifugal filtration, p - nitrophenol is obtained.

[0071] The remaining raw materials and preparation process are the same as those in Example 1.

[0072] Comparative Example 6

[0073] This comparative example is different from Example 1 in that tar is separated by sedimentation in S1. The specific implementation steps are as follows:

[0074] S1. Under the protection of inert gas, p - nitrochlorobenzene and aqueous sodium hydroxide solution are mixed, heated to 160 °C and stirred for 4 h. After the reaction ends, sedimentation is carried out for 72 h to obtain a mixed solution of sodium p - nitrophenolate;

[0075] S2. Under the protection of inert gas, the mixed solution of sodium p - nitrophenolate is mixed evenly with hot water, 30% aqueous hydrochloric acid solution is added, the pH is adjusted to 1.5, the temperature is raised to 80 °C and stirred for 0.5 h, then cooled to 40 °C and stirred for 0.5 h, and then cooled to 25 °C for crystallization. After centrifugal filtration, crude p - nitrophenol is obtained; The crude p - nitrophenol is distilled under reduced pressure at 0.06 MPa to obtain p - nitrophenol.

[0076] The remaining raw materials and preparation process are the same as those in Example 1.

[0077] The yields and purities of sodium p-nitrophenolate and p-nitrophenol prepared in Examples 1 - 6 and Comparative Examples 1 - 6 were determined;

[0078] Note: Yield = actual output / theoretical output * 100%; The purities of sodium p-nitrophenolate and p-nitrophenol were determined by liquid chromatography;

[0079] The results are shown in Table 1:

[0080] Table 1

[0081]

[0082]

[0083] As can be seen from Table 1, through the method for the production and purification of p-nitrophenol provided by the present invention, sodium p-nitrophenolate and tar are separated, and then p-nitrophenol is purified. It can be seen from Comparative Examples 1 - 6 and Example 1 that the yields and purities of sodium p-nitrophenolate and p-nitrophenol are both improved, and the product quality is enhanced. The differences between Examples 2 - 6 and Example 1 are only the adjustment and change of process conditions within a reasonable range. From the results, the yields and purities of sodium p-nitrophenolate and p-nitrophenol are both improved.

[0084] Compared with Example 1, Comparative Examples 1 - 4 are mainly reflected in the purification process of sodium p-nitrophenolate. The p-nitrophenol prepared by using high-purity sodium p-nitrophenolate in subsequent reactions also has corresponding improvements in its yield and purity. Among them, the filtration method replaces the traditional time-consuming and laborious sedimentation method, mainly removing macromolecular polymers; then an extraction method is used to separate small-molecule tar insoluble in water; and then a cooling crystallization method is used to precipitate sodium p-nitrophenolate, which not only achieves the purpose of separating sodium p-nitrophenolate from tar, but also reduces a series of side reactions generated by tar in subsequent reactions; at the same time, unreacted sodium hydroxide is also removed, which can reduce the dosage of subsequent hydrochloric acid solution; Comparing Comparative Examples 4 - 6 with Example 1, the main difference lies in that a single purification method is used for sodium p-nitrophenolate and p-nitrophenol, and a sedimentation method is used to separate sodium p-nitrophenolate and tar. Regarding the influence on the final yield and purity, the results show that the method of filtering - extracting - crystallizing used in Example 1 to separate sodium p-nitrophenolate and tar, and then obtaining p-nitrophenol by vacuum distillation of the crude p-nitrophenol has the best effect.

[0085] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variation thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device.

[0086] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for the production and purification of p-nitrophenol, characterized in that, It includes the following steps: S1. Under the protection of inert gas, p-nitrochlorobenzene and aqueous sodium hydroxide solution are mixed, heated and stirred. After the reaction is completed, filtration is carried out to obtain a reaction solution; an organic solvent is added to the reaction solution, and extraction and separation are carried out to obtain an organic phase and an aqueous phase. The aqueous phase is cooled and crystallized, and centrifugal suction filtration is carried out to obtain a filtrate and sodium p-nitrophenolate; S2. Under the protection of inert gas, sodium p-nitrophenolate is mixed evenly with hot water, hydrochloric acid aqueous solution is added, the pH is adjusted, heated and stirred, cooled and stirred, cooled and crystallized, and centrifugal suction filtration is carried out to obtain crude p-nitrophenol; the crude p-nitrophenol is obtained after vacuum distillation to obtain p-nitrophenol.

2. The method for producing and purifying p-nitrophenol according to claim 1, wherein The temperature of the heating is 150-170 °C; the time of the reaction is 3-4 h.

3. A method for the production and purification of p-nitrophenol according to claim 1, characterized in that, The size of the filter membrane for the filtration is 0.8-3 μm.

4. A method for the production and purification of p-nitrophenol according to claim 1, characterized in that, The volume of the organic solvent is 10%-15% of the volume of the reaction solution; the organic solvent is one of ether and ethyl acetate; both the organic phase and the filtrate can be recycled.

5. A method for the production and purification of p-nitrophenol according to claim 1, characterized in that, In S1, the cooling crystallization of the aqueous phase is to cool to 10-20 °C for crystallization.

6. A method for the production and purification of p-nitrophenol according to claim 1, characterized in that, The concentration of the hydrochloric acid aqueous solution is 25%-35%.

7. A method for the production and purification of p-nitrophenol according to claim 1, characterized in that, The pH is adjusted to 1-2.

8. A method for the production and purification of p-nitrophenol according to claim 1, characterized in that, The heating and stirring is to stir at 60-80 °C for 0.5-1 h; the cooling and stirring is to cool to 40-45 °C and stir for 0.5-1 h.

9. A method for the production and purification of p-nitrophenol according to claim 1, characterized in that, In S2, the cooling crystallization is to cool to 20-30 °C for crystallization.

10. A method for the production and purification of p-nitrophenol according to claim 1, characterized in that, The pressure of the vacuum distillation is 0.05-0.08 MPa.

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